Tandem Blaise/retro-Blaise reaction for the nitrile-mediated regioselective intermolecular addition of unstabilized zinc ester enolates (Reformatsky Reagents) to 1-alkynes and 1,3-enynes

We report the novel use of a nitrile as a mediator to achieve the regioselective intermolecular addition of unstabilized zinc ester enolates (Reformatsky reagents) to 1-alkynes and 1,3-enynes. This reaction is made possible by a reversible addition of enolates to a nitrile (Blaise reaction), generating a zinc aza-enolate that, unlike zinc ester enolates, can add intermolecularly to 1-alkynes and 1,3-enynes. Subsequent removal of the nitrile through a retro-Blaise reaction generates the targeted addition product. This method is combined with a Diels-Alder reaction and subsequent oxidative aromatization, providing a tandem one-pot de novo construction of α-arylated alkanoates from Reformatsky reagents.